Include README.md and LICENSE in the package

LICENSE

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+packages/next-zodenv/LICENSE

README.md

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+packages/next-zodenv/README.md

packages/next-zodenv/LICENSE

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+MIT License
+
+Copyright (c) 2022 Shinya Fujino
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/next-zodenv/README.md

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+# next-zodenv
+
+next-zodenv makes dealing with environment variables in [Next.js](https://nextjs.org/) safer. Its concept is heavily inspired by [envsafe](https://github.com/KATT/envsafe) created by [KATT](https://github.com/KATT), but there are some nuances; you define a schema for your `process.env` with [Zod](https://zod.dev/)'s constructs! In addition, because it's developed to work with Next.js in mind, integrating next-zodenv with Next.js is a piece of cake (it can be used with other environments, though).
+
+Here are the basic ideas of next-zodenv:
+
+* 💎 Express environment variables declaratively using Zod
+* ✅ Validate that the specified environment variables are not missing on build time
+* 🪄 Transform environment variables to the type your application expects
+* 🤝 Work on Node.js and the browser
+
+## Setup
+
+```sh
+npm install next-zodenv zod
+```
+
+## Usage
+
+Suppose that you have the following environment variables:
+
+```
+FOO="server_only_variable"
+PORT=3000
+API_URL="https://example.com/api"
+NEXT_PUBLIC_VAR="public_variable"
+```
+
+You can define a schema for your environment variables:
+
+```ts
+import { zenv } from 'next-zodenv'
+import { z } from 'zod'
+
+const env = zenv(z.object({
+  FOO: z.string(),
+  PORT: z.preprocess(Number, z.number().int().gte(1).lte(65535)),
+  API_URL: z.string().url(),
+}))
+
+env.FOO             // string
+env.PORT            // number (1-65535)
+env.API_URL         // string (URL)
+env.NEXT_PUBLIC_VAR // undefined
+```
+
+Note that types other than string must be transformed with [`z.preprocess`](https://github.com/colinhacks/zod#preprocess) beforehand. This is because environment variables are always string and we need to transform them to the type Zod's schema expects.
+
+For simple cases like the above, next-zodenv offers built-in validators defined using Zod's constructs:
+
+```ts
+import { zenv, str, port, url } from 'next-zodenv'
+import { z } from 'zod'
+
+const env = zenv(z.object({
+  FOO: str(),
+  PORT: port(),
+  API_URL: url(),
+}))
+```
+
+The complete list of built-in validators is as follows:
+
+Validator | Zod schema
+--- | ---
+`str()` | `z.string()` 
+`bool()` | `z.preprocess((val) => val === 'true', z.boolean())`
+`num()` | `z.preprocess(Number, z.number())`
+`port()` | `z.preprocess(Number, z.number().int().min(1).max(65535))`
+`url()` | `z.string().url()`
+`email()` | `z.string().email()`
+
+### Next.js
+
+In order to expose environment variables to the browser in Next.js, you need to pass the `nextPublic` property to `zenv` like this:
+
+```ts
+const env = zenv(
+  z.object({
+    NEXT_PUBLIC_VAR: z.string(),
+  }),
+  {
+    nextPublic: {
+      NEXT_PUBLIC_VAR: process.env.NEXT_PUBLIC_VAR,
+    }
+  },
+)
+
+env.NEXT_PUBLIC_VAR // available in the browser
+```
+
+To validate on build time and stop the build process if there are missing environment variables, load your schema in `next.config.js`:
+
+```ts
+// next.config.js
+const { env } = require('./env/server.js');
+
+// ...
+```